"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:f99c58e8-a618-46e7-a3e0-76d286109c5a","http://resolver.tudelft.nl/uuid:f99c58e8-a618-46e7-a3e0-76d286109c5a","Design Considerations for the Glenohumeral Prosthesis","Oosterom, R.","Beukers, A. (promotor); Rozing, P.M. (promotor)","2005","The shoulder joint provides us with a large range of motion. This is enabled by the shallowness of the glenoid cavity and the cooperation of many bone elements of the shoulder girdle. This results in complex biomechanics and dependency to surrounding soft tissues for its stability. Due to a fracture or joint diseases, a shoulder replacement may have to be performed, aiming at removing the excessive pain and to restore joint functionality. Especially post-operative joint functionality is not sufficient to perform tasks of daily living and many post-operative complications occur. Results must be improved, which, among others, can be achieved by design improvements. To restore the natural anatomy, the anatomical glenohumeral prosthesis is used, of which the geometry, insertion and fixation have been investigated. Parallel, a conceptually new design is developed, proposed for patients for whom no long lasting reliable solution is available. This design focuses on integration of lost anatomical functions with improved fixation techniques","shoulder prosthesis; design; stability","en","doctoral thesis","Delft University Press","","","","","","","","Aerospace Engineering","","","","",""
"uuid:c0cb51f7-dc9f-418e-b80d-a312e9f3b6b5","http://resolver.tudelft.nl/uuid:c0cb51f7-dc9f-418e-b80d-a312e9f3b6b5","Aero-elastic Stability Analysis for Large-Scale Wind Turbines","Meng, F.","Van Tooren, M.J.L. (promotor)","2011","Nowadays, many modern countries are relying heavily on non-renewable resources. One common example of non-renewable resources is fossil fuel. Non-renewable resources are ?nite resources that will eventually dwindle, becoming too expensive or too environmentally damaging to retrieve. In contrast, renewable energy resources, like wind energy, are constantly replenished and are important because of the bene?ts it provides for us as well as for our environment. However, getting the energy from wind must be further investigated in order to make the usage of wind energy more economically. During the past thirty years, the trend in wind energy is to increase the size of wind turbines for producing more electricity power with lower cost. The increase in size is bene?cial in terms of reduction of manufacturing costs per kW hours and reduction of the ground surface occupied by the wind farms. Further increases in size are not easily achievable because designers are expected to face more unknown technical problems such as aero-elastic stability problems. Therefore, it is important to investigate the aero-elastic stability problem of each new design concept in order to prevent the damage happen. In practice the larger blades have a lower edge-wise frequency that is closer to the ?ap-wise frequency than the case for the smaller blades. This could result in bigger edge-wise vibrations and unexpected aero-elastic problems. Larger blades will also result in large deformations even when the wind turbines are running at the design condition. Furthermore, designing pitch-regulated wind turbines will often result in lightweight and very ?exible blades. The effects of large and ?exible blade are mainly reducing diameter of the rotor during operation and coupling between edge-wise and torsional forces and motion. Most aero-elastic codes for wind turbines do not consider the e?ects of large de?ections in their simulation of the loads and responses. The reduced effective rotor area leads to lower power production than predicted by linear calculations and the coupling between edge-wise and torsional forces and motion will increases pitch moment at the blade pitch system. The problems mentioned above are the current research problems needed to be investigated and solved due to upscaling of the wind turbines. In this research work, nonlinear ?exible multi-body dynamics has been chosen to couple with nonlinear aerodynamics to investigate the current research problems mentioned before. An aero-elastic simulation tool called MBDyn-AeroDyn is developed by integration of two existing code named MBDyn [1] and AeroDyn [2]. MBDyn is a nonlinear ?exible multi-body dynamic code, which can simulate the effect of large de?ections and large rotations. The aerodynamic forces acting on wind turbine blades are calculated using AeroDyn which is based on the blade element-momentum theory. Improvement of aerodynamic calculation has been made by adding a modi?ed Pitt-Peters dynamic in?ow model in AeroDyn. Afterwards, both a linear time invariant system identi?cation method and a linear time periodic system identi?cation method have been used and implemented to investigate the aero-elastic stability of multi-MW wind turbine blades. Finally wind tunnel measurements have been performed in order to validate the aero-elastic simulation tool developed in this work. The validation of this aero-elastic simulation code has been carried out in this thesis. The time domain simulation results show that this aero-elastic simulation tool has good agreement with wind tunnel experiment results at the design operation condition. For the offdesign cases, the differences become larger gradually. Further more, an aero-elastic simulation has been applied on a 5MW wind turbine. Comparison has been made between FAST and BLADMODE in time domain. The results show that MBDyn-AeroDyn and FAST have a good agreement for an uniform wind ?eld. Finally, ?ap-torsion ?utter analysis on the 5MW wind turbine has been performed. The main feature of this aero-elastic simulation tool for multi-MW large horizontal axis wind turbines developed in this work is that kinematically large displacements and rotations are included, and that loads are applied on the deformed geometry. This allows the designers to simulate large wind turbines with more ?exible blades to capture the effect of large displacements and rotations more accurately. Another feature is that both a linear time invariant system identi?cation method and a linear time periodic system identi?cation method have been implemented. It allows the designers to analyse stability from the time domain simulation data. From the result of ?ap-torsion ?utter analysis on the 5MW wind turbine, it is shown that ?ap-torsion ?utter is not likely to occur on this 5MW wind turbine with the current blade structural properties and intended operating conditions. Considering with the current Ph.D works which have been done so far, ?rstly, another wind tunnel experiment maybe necessary by using the same blades. Future measurement should be made at a higher rotation speed and combined with higher wind speed in order to ?nd the stability boundary of this model wind turbine. Secondly, this aero-elastic simulation tool should be integrated into a knowledge based engineering(KBE) wind turbine blades design environment in order to take advantage of this aero-elastic simulation tool. Further research work should be carried out to simulate wind turbine blades with smart control devices, for example, ?aps on the blades. Last but not the least, an user friendly graphical interface for this tool should be made in order to make it more convenient to use for a wider group of users.","wind turbine simulation; aero-elastic; stability","en","doctoral thesis","","","","","","","","","Aerospace Engineering","Aerospace Design, Integration & Operations","","","",""
"uuid:2ce88658-a4c3-459f-afdc-00a5ac2c4ac4","http://resolver.tudelft.nl/uuid:2ce88658-a4c3-459f-afdc-00a5ac2c4ac4","Degradation of CIGS solar cells","Theelen, M.J.","Zeman, M. (promotor)","2015","Thin film CIGS solar cells and individual layers within these solar cells have been tested in order to assess their long term stability. Alongside with the execution of standard tests, in which elevated temperatures and humidity levels are used, the solar cells have also been exposed to a combination of elevated temperature and humidity and illumination, which also allowed in-situ analysis of the changes in the electrical parameters. Additionally, the samples have been tested in the presence of water and various atmospheric species, like CO2, nitrogen and oxygen, in order to assess the impact of these species. Based on these experiments, it was concluded that CIGS solar cells can rapidly lose efficiency due to the migration of sodium, which occurs when exposed to illumination and water vapor. It was also observed that the transparent top electrode, consisting of ZnO:Al degraded rapidly in the presence of a combination of water and CO2, while it is stable in the presence of water combined with e.g. N2 and O2. The thesis also contains an extensive literature study on the stability of CIGS solar cells and a study on the temperature dependency of these solar cells.","CIGS; solar cell; molybdenum; zinc oxide; stability; reliability; lifetime; in-situ testing; illumination; damp heat; ZnO:Al; CO2; temperature dependency","en","doctoral thesis","","","","","","","","2015-09-05","Electrical Engineering, Mathematics and Computer Science","PhotoVoltaic Devices and Materials","","","",""
"uuid:6a4cd23e-b791-4bc4-acc6-a7011cdb85bd","http://resolver.tudelft.nl/uuid:6a4cd23e-b791-4bc4-acc6-a7011cdb85bd","Identification of Spinal Reflexes","De Vlugt, E.","Van der Helm, F.C.T. (promotor)","2004","Visco-elasticity of joints is important for the maintenance of the human body posture and can in two manners be regulated. By means of cocontraction of antagonistic muscle groups and by neural reflexive feedback of muscle length and muscle strength, measured both by means of sensors in the muscles. The impact of the reflexive regulation is considerable and infestation of this system can give serious motor deviations, like at the Parkinson's Disease. Except anatomical knowledge is there still little clear concerning of the functionality of reflexes. This comes because there is no adequate measurement technique during natural movements to quantify the neuromuscular system. During my promotion research I have developed and applied experimental techniques with which the gain of several neural feedback pathways can be measured. Techniques have been developed for posture tasks and have been applied on the human arm. The results indicate that the reflexive system is highly adaptable and under certain circumstances works as an optimum controller. There seems to be a trade-off between two contrary properties: the magnitude of the visco-elasticity and the dynamic stability of the joint. Or, high reflexive feedback gains are desirable but are possible that mechanical oscillation occurs due to the neural time delay of the reflexive system. Such a dynamic analyses are new and make it possible to study the role of reflexes during natural movement. Benefits of this study ranges from new fundamental issues to clinical diagnostic tools.","reflexive control; human arm; posture maintenance; system identification; stability","en","doctoral thesis","","","","","","","","","Design, Engineering and Production","","","","",""
"uuid:25ca8f8e-d0af-42a4-bd39-5bc609cf2bc6","http://resolver.tudelft.nl/uuid:25ca8f8e-d0af-42a4-bd39-5bc609cf2bc6","Piezo-driven stages for nanopositioning with extreme stability: Theoretical acpects and practical design considerations","Van der Wulp, H.","Van Beek, H.F. (promotor)","1997","","nanopositioning; stability; Piezo actuators; capacitive transducers","en","doctoral thesis","Delft University Press","","","","","","","","Mechanical Maritime and Materials Engineering","","","","",""
"uuid:67e84328-459e-40e0-8fdf-397ee9eedaf0","http://resolver.tudelft.nl/uuid:67e84328-459e-40e0-8fdf-397ee9eedaf0","Re-entry flight clearance","Juliana, S.","Mulder, J.A. (promotor)","2006","The objective of the research was to identify and evaluate promising mathematical techniques for re-entry flight clearance. To fulfil this objective, two mathematical methods were investigated and developed: μ analysis for linear models and interval analysis for both linear and non-linear models. The stability of re-entry vehicles in the presence of model uncertainties was chosen as the clearance criterion, which is represented by two mathematical criteria: worst-case eigenvalues (linear) and the Lyapunov stability (non-linear). Two vehicle models including flight control systems were developed and used as case studies for the evaluation of the clearance techniques. These models are based on the DART (Delft Aerospace Re-entry Test Demonstrator) and SPHYNX (Subscale Precursor Hypersonic X) re-entry vehicle models. The suitability of the two mathematical techniques for re-entry flight clearance was evaluated based on the results of the clearance application on these models. Non-linear simulations were also performed to verify the clearance results generated by the two techniques. Non-linear interval analysis has been found to be the most reliable method of all other methods investigated in this research, because it could perform the clearance for the non-linear dynamic models of the re-entry vehicles with uncertainties, and the results were confirmed by the non-linear simulations.","stability; robustness; closed-loop system; nonlinear; lyapunov function; interval; clearance; re-entry","en","doctoral thesis","","","","","","","","","Aerospace Engineering","","","","",""
"uuid:0c57ceb6-00b7-4434-9fee-a391208fe005","http://resolver.tudelft.nl/uuid:0c57ceb6-00b7-4434-9fee-a391208fe005","Evolution of morphology in solidifying aluminium alloys","Dijkstra, W.O.","Katgerman, L. (promotor); Vuik, C. (promotor)","2007","In the thesis two different models of solidification of aluminum alloys are presented and analyzed. The first 1--D solidification model is derived from the conservation of solute, heat and mass. With numerical experiments it is shown that simulations with the Finite Difference discretization must adhere a relation similar to the Courant-Friedrichs-Lewy relation in order to get numerical stable solutions. Furthermore, it is demonstrated that depending on the chosen discretization of the interface conditions an additional singularity which can destroy stability occurs. The occurrence of this singularity is not related to the Finite Difference discretization. Singularities are also found with application of the Collocation Method. An example of a solidifying aluminum slab is successfully solved with application of the model equations and avoiding stability infringements. The possibility to apply the model in an extended simulation, i.e. especially in the second solidification model, is discussed. The second new 2--D solidification network model is used to simulate fluid flow and solidification within the mush. It is based on the assumption that the liquid parts of the mush can up to some degree be represented by a network of geometrical simplified liquid channels. Numerical simulations with this model indicate that conduction and convection of heat and solute affects directly only the permeability of a small region of the mush. Self induced effects and the formation wormholes have not been found. Finally, a detailed study of the influence of various model parameters of the network model is presented. A more detailed abstract is included within the thesis.","solidification; aluminium; permeability; mushy zone; stability; modeling","en","doctoral thesis","","","","","","","","","Mechanical Maritime and Materials Engineering","","","","",""
"uuid:8c4240fb-0315-462a-8b3b-efbd0f0e68b6","http://resolver.tudelft.nl/uuid:8c4240fb-0315-462a-8b3b-efbd0f0e68b6","Energy-free systems: Theory, conception, and design of statically balanced spring mechanisms","Herder, J.L.","Cool, J.C. (promotor)","2001","","Static balance; stability; mechanism design; energy-efficiency","en","doctoral thesis","","","","","","","","","Mechanical Maritime and Materials Engineering","","","","",""
"uuid:25fbc401-50f7-42a5-ac2c-2b4e0e00dc10","http://resolver.tudelft.nl/uuid:25fbc401-50f7-42a5-ac2c-2b4e0e00dc10","Stability, Accuracy, and Robustness of the Time Domain Integral Equation Method for Radar Scattering Analysis","Van 't Wout, E.","Vuik, C. (promotor)","2013","The aim of this thesis is to design a computational method that can be used in modern stealth technology. In particular, the computational method should be capable to simulate scattering of ultra-wideband radar signals for military aircraft constructed with ferromagnetic radar absorbent materials. A full-wave boundary element method has been chosen because of its efficiency for electromagnetic scattering of electrically large structures. A time-domain method has been chosen because wideband signals can be simulated with a single run. Moreover, the future use of nonlinear constitutive equations for ferromagnetic materials requires simulation in time domain. To this end, the Time Domain Integral Equation (TDIE) method is used as computational method. More specifically, the numerical discretization of the Electric Field Integral Equation (EFIE) is given by the Marching-on-in-Time (MoT) scheme, which has been chosen because of its efficiency and accuracy. Instabilities prevent its industrial application to stealth technology, even for smallband and linear constitutive equations. In this thesis, a thorough numerical analysis on stability, accuracy, and robustness has been derived, resulting in clear guidelines for the choice of numerical parameters. Consequently, stable computer simulations have been achieved.","radar scattering; computational electromagnetics; boundary element method; integral equation method; time domain; numerical analysis; stability; accuracy; robustness","en","doctoral thesis","","","","","","","","2013-11-11","Electrical Engineering, Mathematics and Computer Science","Delft Institute of Applied Mathematics","","","",""
"uuid:629d48cd-8777-40ac-a466-622df6cfa7ce","http://resolver.tudelft.nl/uuid:629d48cd-8777-40ac-a466-622df6cfa7ce","Experimental and numerical stability investigations on natural circulation boiling water reactors","Marcel, C.P.","van der Hagen, T.H.J.J. (promotor)","2007","The stability of natural circulation boiling water reactors is investigated with a strong emphasis on experiments. Two different facilities are used for such a task: the GENESIS facility (to which a void reactivity feedback system is artificially added) and the CIRCUS facility. In addition, numerical codes are also used in the investigation.","stability; neutronic-thermal-hydraulic coupling; fluid-to-fluid scaling; boiling; flashing","en","doctoral thesis","IOS Press","","","","","","","","Applied Sciences","","","","",""
"uuid:9a855740-09c1-4af5-bf06-355ba6b2b619","http://resolver.tudelft.nl/uuid:9a855740-09c1-4af5-bf06-355ba6b2b619","Stability of the shoulder: Intrinsic muscle properties and reflexive control","Rozendaal, L.A.","Stassen, H.G. (promotor); Rozing, P.M. (promotor); Van der Helm, F.C.T. (promotor)","1997","","shoulder; stability; muscle; posture maintenance; reflexive control","en","doctoral thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","","","","",""
"uuid:a8df2c53-6228-45f4-a509-8f59561dab50","http://resolver.tudelft.nl/uuid:a8df2c53-6228-45f4-a509-8f59561dab50","Stability of fishing vessels in waves and wind","Laureano, Jose Luis Mantari","","2010","","hydrodynamics; Fishing vessels; waves; wind; stability","","doctoral thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Marine and Transport Technology","Ship Hydromechanics and Structures","","",""
"uuid:e35c4735-1f6f-4e4c-b7b8-130f68a7dd02","http://resolver.tudelft.nl/uuid:e35c4735-1f6f-4e4c-b7b8-130f68a7dd02","Reducing the cover-to-diameter ratio for shallow tunnels in soft soils","Vu Minh, N. (TU Delft Geo-engineering)","Bosch, J.W. (promotor); Broere, W. (copromotor)","2016","Despite the fact that shallow tunnels have the benefits of low short-term construction costs and long-term operational costs primarily due to the shallow depth of the station boxes, the limited understanding of shallow tunnelling in soft soils is an obstacle to the development of shallow tunnels in urban areas. This study carries out a theoretical investigation of the effects of reducing the cover-to-diameter ratio C/D for shallow tunnels in soft soils.In stability analysis, the uplift, face stability and blow-out mechanisms are investigated. This study investigates interactions between the TBM and surrounding soil in tunnelling process, the stability of the TBM is not taken into account. The relationship between the C/D ratio and the required thickness-to-diameter ratio d/D as well as the required support pressures will be derived in various soils. Ranges of support pressures are also estimated for the TBM.Structural analysis is carried out for the variation of deformations and internal forces of the tunnel lining when reducing the C/D ratio. Since the conventional design models are not suitable in the case of shallow tunnels a new structural analysis model, which includes the difference between loads at the top and at the bottom of the tunnel, is proposed. Optimal C/D ratios with various d/D ratios for shallow tunnels in soft soils are also derived.With respect to ground movement analysis, this research investigates the areas affected by shallow tunnelling with a preliminary assessment of the risk of building damage by investigating surface and subsurface soil displacements. These areas are determined for different tunnel diameters in various soil types and are then compared to recent studies.The total volume loss is estimated at the tunnelling face, along the TBM, at the tail and includes long-term consolidation settlements. By combining empirical models from the literature and the proposed new models, the volume loss components are estimated both for short-term construction and for the long-term consolidation effects. This shows that a no volume loss is feasible in shallow tunnelling with careful control of the support pressure.The boundaries of the influence zones in shallow tunnelling are identified and discussed on the basis of various case studies. The effects of the soil parameters on the influence areas are also investigated.From these calculations, the limits and optimal C/D ratios for shallow tunnelling are deduced and recommendations and solutions for improving the shallow tunnelling process are proposed in this dissertation.